Avisynth MixAudio Failure

[InvonativePercushion]

I have two video files in which I just can not seem to be able to mix audio, here is the code:

#InvonativePercushion
bricks=AVISource("C:\Users\Owner\Videos\Music with Everyday Objects\Bricks.avi").Trim(1080,1080+1116)
laundry=AVISource("C:\Users\Owner\Videos\Music with Everyday Objects\Laundry.avi").Trim(1215,1215+1116)
b_audio = BlankClip(bricks, audio_rate=48000)
AudioDub(bricks, b_audio)
l_audio = BlankClip(laundry, audio_rate=48000)
AudioDub(laundry, l_audio)
KillVideo(b_audio)
KillVideo(l_audio)
aud=mixaudio(b_audio,l_audio)
return aud

It returns a black screen (expected) with no audio whatsoever (unexpected). Why is this so, and what can I do to fix it?

[Gavino]

b_audio and l_audio both contain only silence, so mixing them gives silence too.

Note that variables are only changed via assignment.
A statement such as KillVideo(b_audio) does not change b_audio, it assigns its result to the special variable last.

Assuming bricks and laundry have the same sample rate, all you need is:

bricks = ...
laundry = ...
aud = MixAudio(bricks, laundry)
return AudioDub(BlankClip(bricks), aud)